An optical network is a system for communicating information over optical fiber using optical transmitters (including, for example, lasers), which transmit data-carrying optical signals over optical fiber links to optical receivers.
In optical networks extending over relatively large distances, the optical signals may be attenuated. Accordingly, optical amplifiers may be provided along the optical fiber link to amplify or boost the power of the transmitted optical signals.
If a break or fault occurs in the optical fiber link, the optical amplifiers provided along the optical fiber link are preferably deactivated or shut-down, so that, for example, a technician may safely repair the break or fault. After the break has been repaired, link recovery processes can be performed and the optical transmitters can then resume transmission of optical signals on the optical fiber link.
Optical amplifiers may be provided at different locations along the optical fiber link. For example, optical amplifiers may be substantially co-located with an optical transmitter to amplify the output of the optical transmitter. The optical transmitter may also include an optical amplifier. Further, optical amplifiers may be substantially co-located with an optical receiver to amplify the optical signals supplied thereto, and the optical receiver itself may have an optical amplifier. For convenience, optical amplifiers provided at the input of an optical receiver may be referred to herein as “preamplifier amps,” and optical amplifiers provided at the output of an optical transmitter may be referred to herein as “booster amps.”
In order to convey link status or other monitoring and control information in an optical communication system, an optical service channel (OSC) may be provided that carries such information over an optical signal having a wavelength different than the above-noted data-carrying optical signals. The OSC may be transmitted from one network element to the next along the optical fiber link. At each network element, the OSC may be demultiplexed or separated from the other optical signals and converted to a corresponding electrical signal, which is then processed, and retransmitted, often with updated monitoring and control information. As a result, each network element connected along the optical fiber link may receive information about other network elements, such that monitoring information is distributed along the link.
Preferably, control and monitoring information should be distributed as rapidly as possible along the optical fiber link. Booster and preamplifier amps may, like other network elements, process the control and monitoring information, and thus may slow propagation of the OSC. One solution to increase the speed of propagation of the OSC would be to provide booster and preamplifier amps in which the OSC passes through such optical amplifiers without optical-to-electrical conversion. Such booster and preamplifier amps, however, would have a construction different than that of other amplifiers coupled to the fiber optic link. As such, the same optical amplifiers may not be used for booster and non-booster applications (e.g., at locations spaced from transmitter and receivers, such as a line amplifier, as well as in the transmitters and receivers themselves). There is a need, therefore, for a standard optical amplifier that may be used as a both a booster amp and a line amplifier. Further, there is a need that for such an optical amplifier that can rapidly pass an OSC when provided as an booster or preamplifier amp.